Preplasmic expression of a tandem scvf antibody for simultaneous targeting of two immune check-points

Introduction: Immune checkpoints are regulators contributing in self-tolerance and helping immune homeostasis. However, some cancer cells activate them to prevent anti-tumor immune response. Immune check-points inhibitors have been proposed to help immune system identify andkill tumor cells with promising results in clinic practice. . Here, we aimed to produce a novel bispecific antibody (tandem scvf) originated from nivolumab and ipillimumab for simultaneous targeting CTLA-4 and PD-1 check-points.Methods: Thebispecific tandem scvf antibody gene was designed based on amino acid sequences of variable regions of parent antibodies and codon optimized for expression in bacterial system. Synthetic gene was ligated into suitable expression vector (pET22b) before pripaslmic signal peptide. E. coli BL21 (DE3) was used as a host cell for protein expression.Protein expression at different temperatures (23, 30, 37 ºC) and with different inducer concentrations (0.1, 0.5, 1 mM) was done. After periplasmic extraction, antibody was purified by affinity-chromatography.Results: Expression of tandem scvf antibody (60 kDa) was confirmed by SDS-page and western blot. The optimum expression condition was found to be induction with 0,5 mM IPTG and incubation at 30 ºC. Biological assay of purified antibody is is going to be performed by the research group.Conclusion: Optimization of expression condition could improve periplasmic expression of scfv antibody. This scvf could be a potential candidate to targeting immune check-points, although in vitro and in vivo biological function evaluations still need to be performed.